Catch dog Jaw Muscle Cramp??????

Dogs are not prone to get tetanus but from what I remember, lock jaw is a symptom. Highly doubt it's such a thing as tetanus but then again, I've not heard of your perdicument either. I would treat the muscles same as if the dog was human. Apply some heat for ten minutes or so to the jaw muscles, then apply inward pressure with your thumb to stretch the muscle out same way a messeure would work out a knot in your muscle ( ten min of this won't be near long enough messeure will work on a knot for a while) and then see if the dog has much better movement of its jaw. May need to repeat couple times a day if thus is working and doesn't fix it on the initial session. If this doesn't help, I'd start calling and talking to vets to try to find one who is competent in this area and can solve your problem instead of going to the local vet and have them guess as to the problem and how to solve.